feat: add ConfigModule and FakeBackendInterceptor

Closes #34, #37

src/environments/environment.prod.ts

@@ -13,5 +13,7 @@
  * this program. If not, see <https://www.gnu.org/licenses/>.
  */
 export const environment = {
-  production: true
+  backend_url: 'http://localhost:3000',
+  backend_version: '1.0.0',
+  production: true,
 };